Drafted by the Eagles in January 1989 after a season playing seniors, but returned to Melbourne a few months later after a handful of games with the East Perth colts side.

The defender wore number 38 in 1990 but only played three Reserves games while concentrating on his studies. He also played for Wangaratta Rovers during 1990, but was delisted by the Demons when he refused to move to the city permanently.

Williamson then played for Golden Square in 1991, went back to Wangaratta again in 1992 and 1993, then played for Lakes Entrance until 1995 and North Wangaratta from 1997 to 2002, where he also coached in his last year.